1 from unittest import TestCase

     2 

     3 import json

     4 

     5 class JSONTestObject:

     6     pass

     7 

     8 

     9 class RecursiveJSONEncoder(json.JSONEncoder):

    10     recurse = False

    11     def default(self, o):

    12         if o is JSONTestObject:

    13             if self.recurse:

    14                 return [JSONTestObject]

    15             else:

    16                 return 'JSONTestObject'

    17         return json.JSONEncoder.default(o)

    18 

    19 

    20 class TestRecursion(TestCase):

    21     def test_listrecursion(self):

    22         x = []

    23         x.append(x)

    24         try:

    25             json.dumps(x)

    26         except ValueError:

    27             pass

    28         else:

    29             self.fail("didn't raise ValueError on list recursion")

    30         x = []

    31         y = [x]

    32         x.append(y)

    33         try:

    34             json.dumps(x)

    35         except ValueError:

    36             pass

    37         else:

    38             self.fail("didn't raise ValueError on alternating list recursion")

    39         y = []

    40         x = [y, y]

    41         # ensure that the marker is cleared

    42         json.dumps(x)

    43 

    44     def test_dictrecursion(self):

    45         x = {}

    46         x["test"] = x

    47         try:

    48             json.dumps(x)

    49         except ValueError:

    50             pass

    51         else:

    52             self.fail("didn't raise ValueError on dict recursion")

    53         x = {}

    54         y = {"a": x, "b": x}

    55         # ensure that the marker is cleared

    56         json.dumps(x)

    57 

    58     def test_defaultrecursion(self):

    59         enc = RecursiveJSONEncoder()

    60         self.assertEquals(enc.encode(JSONTestObject), '"JSONTestObject"')

    61         enc.recurse = True

    62         try:

    63             enc.encode(JSONTestObject)

    64         except ValueError:

    65             pass

    66         else:

    67             self.fail("didn't raise ValueError on default recursion")